By Bill Moore
If you're old enough to remember the hit television series 'Mork and Mindy,' you'll recall that the favorite expression of the alien played by Robin Williams was, "nannu, nannu."
Now this piece of 80's television sitcom trivia has absolutely nothing to with molecular scale structures, but seemed a fun way to introduce one of the most intriguing areas of current scientific research: nanotubes. One can almost imagine that unlike we common mortals, Robin Williams' frenetic brain is already hardwired with nano-scale circuitry, clearly operating at quantum levels of expression.
In fact, that's one reason why researchers at IBM and AMD are investigating nano structures that might someday replace conventional microchip designs. But this story is about the potential promise of storing significant quantities of hydrogen safely and efficiently with atomic-scale sponges made up of nanotubes.
One of the companies in hot pursuit of nano technology is Nanomix, formerly Covalent Materials, Inc. of Emeryville, California. The company was founded by two the pioneers in nano-scale material sciences, Dr. Alex Zettl and Dr. Marvin Cohen, both professors of physics at UC Berkeley.
Nanotubes were first discovered in 1991 by Japanese researcher Sumio Iijima. He was studying a tiny bit of common soot through an electron microscope and noticed an odd filament-like structure. It turned out to be a very long thread measuring just 10 nanometers in diameter and consisting of pure carbon in a form never before seen, similar to the ones in the accompanying photograph above, courtesy of Nanomix.
That discovery launched what can Nanomix's Jeff Wyatt described as the next "land rush" in science and engineering.
EV World first asked Wyatt to explain what exactly is a 'nano.'
"Nano means one billionth. So a nanometer is one-billionth of a meter and that's about ten times as large as the hydrogen atom to put it in perspective," he said, adding that, "at this size scale, the properties of materials begin to exhibit the so-called quantum effect. Things begin to get a little different down there and it's a highly challenging area of science where biology, chemistry and physics converge."
Assuming companies like Nanomix can master technologies at this incredibly small scale, Wyatt and his colleagues believe it will revolutionize material sciences in the next ten to twenty years. "This is where the breakthrough products in electronics, biotechnology [and] new materials are going to come from."
Certainly the storage of hydrogen needs a breakthrough. At present, the most promising way to store it is in super-high-strength cylinders, some the size of a small hot water heater. The gas is compressed at anywhere from 3,500 psi to the current state-of-art at 10,000 psi. The higher the pressure, the more gas, the further the fuel cell vehicle can travel; and the greater the potential of a catastrophic explosion.
It's All About Surface Area
What if instead of compressing it to 10,000 pounds per square inch, you could create a metallic "sponge" that soaked up hydrogen, storing it safely in a low pressure tank of any shape you wish. This is what companies like Ovonics, Hera and Nanomix are trying to do, using different materials from metal hydrides to carbon nanotubes.
Wyatt explained why his company thinks nanotubes appear the best long-term candidate for this task. It's really all about surface area. He said that one pound of carbon nanotubes has the equivalent surface area of 200 American football fields, each measuring 360 feet (110 meters) by 160 feet (49 meters). This works out to be 11,520,000 square feet or 1,078,000 square meters of surface area!
"This is one of the fantastic properties nano structure materials have. The question is, how can you take advantage of that unique property?"
Nanomix has come up with one promising way to do just that. Wyatt illustrated how this might work by using the example of a cold glass of water. He said that just as water vapor will condense on the side of the glass on a warm day, so will hydrogen 'stick' to cold nanotubes.
"That's the key here is this ultra high surface area and you get the hydrogen molecules to begin to stick to that surface," he said. "It's a very simple concept really, but would be impossible without these new nano materials like carbon nanotubes.
How cold is "cold"? According to Wyatt, you'll have to cool the hydrogen down to 80 degrees Kelvin or about minus 200 degrees. This will super-cool the carbon nanotubes and let the hydrogen stick to it.
In contrast, liquid hydrogen used in rockets or in BMW's experimental hydrogen-fueled 745H series sedans has to be cooled to 20 degrees Kelvin above absolute zero. Wyatt explained that this is a factor of "four or five" times colder than required for the carbon nanotube system.
While Wyatt admits 80 degrees Kelvin is still extremely cold, he said that Nanomix is also studying other nano-scale materials that don't have to be cooled as much. Some of these materials have been photographed by an electron-scanning microscope and can be seen on the company's web site in its Photo Gallery section. [Wyatt explains some of the black & white photos in the audio portion of the interview at about 7 minutes into part one.]
In Pursuit of Moore's Law
It was the pursuit of Moore's law - - named after Gordon Moore - - that led scientists like Cohen, Zettl and Iijima to look closer and closer at the very structure of matter. It is generally believed that Moore's law predicts the doubling of computer power every 18 months as micro circuits get smaller and smaller.
This race inspired companies to build increasingly more powerful microscopes including a new class called atomic force microscopes. This permitted chip researchers see right down to the molecular levels of their chip sets and made possible discovers of new compounds and eventually carbon nanotubes.
But discovering new materials by accident is one thing, manufacturing them with any consistency is quite another, it turns out. According to Wyatt, initially, people experimented with making carbon nanotubes by putting a small bit of carbon in a furnace and literally blowing it up with a high-powered laser.
As Wyatt pointed out, this approach isn't very efficient so for the last few years researchers, including those at Nanomix, have been investigating ways to produce carbon nanotubes affordably and efficiently.
"The most promising [method] is called chemical vapor deposition," he said.
The process works this way. You feed natural gas into a heated reactor you've seeded with nano-sized catalyst particles. The natural gas 'condenses' on to the catalyst and forms nanotubes.
"It's fairly simply. It's fairly elegant and it can be scaled up to large production."
Wyatt noted that for purposes of storing hydrogen, the nanotubes don't have to be as highly structured as nano 'turf.' It can, in fact, be more disordered because what is most important is the surface area.
"In the end, we don't care if the tubes are damaged. In fact, in some of the materials that we're looking at aren't even tubes at all. They just have this nano structure and very, very high surface area."
Five To Ten Great Ideas
EV World asked Wyatt to talk briefly about the company, which began only two years ago.
"We thought we had at least five and maybe as many as ten great ideas to start businesses. And today we are working on two projects. We are working on hydrogen storage on nano-structured materials and we are working on a nano-electronics project."
In a brief moment of unusual candor, Wyatt admitted that the company - - at the urging of its investors - - has been wrestling with which project to pursue since both seem so promising, but the money is limited.
"There is a billion dollar-plus market for chemical sensors out there and the technology that we have will leap-frog existing technology and ultimately allow us to move some of these products into the biotechnology, biotech sensing area. So, it's a very, very promising area.
"And likewise" he continued, "the emerging fuel cell industry I think will create a demand for hydrogen storage products that could be as much as a billion dollar market ten years from now."
Continued Next Week. . .
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